1. Field of the Invention
The present invention relates to a control device and a control method for an internal combustion engine (engine) including a plurality of cylinders, which are capable of detecting a misfire state in each of the plurality of cylinders.
2. Description of the Related Art
In recent years, it is required even for motorcycles to detect a misfire state in order to prevent exhaust gas from degrading as counter measures against environmental problems or in order to protect a catalyst provided on an exhaust system of an internal combustion engine.
On this occasion, regarding the detection of the misfire state, there has been proposed a misfire detection device for multi-cylinder engine that is configured to, in a case where such a high misfire rate that damages the catalyst is detected, cut a fuel or change a throttle opening degree to a limited opening degree used when a misfire state is detected in order to limit the speed of a vehicle (see, for example, Japanese Patent No. 4424178).
However, the conventional technology has the following problems.
In the case where the conventional misfire detection device is applied to a lightweight vehicle such as a motorcycle, if the fuel cut is immediately carried out or if the throttle opening degree is immediately changed to a limited opening degree used when a misfire is detected, an abrupt attenuation in torque may occur to generate a shock on the vehicle, resulting in degradation in drivability.
Moreover, upon recovery from the fuel cut or the throttle limited opening degree, an abrupt increase in torque may occur to degrade the drivability. Further, if a detection error occurs in the detection of the misfire state due to interference or the like, a sudden fuel cut is carried out or the throttle opening degree is changed to the throttle limited opening degree during a normal travel, with the result that an abrupt change in torque may occur to degrade the drivability.